Re: [Xen-devel] [PATCH v9 5/5] xen/tools: VM forking toolstack side

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Mon, Feb 24, 2020 at 9:30 AM Julien Grall <julien@xxxxxxx> wrote:
>
> Hi,
>
> On 24/02/2020 16:19, Tamas K Lengyel wrote:
> > On Mon, Feb 24, 2020 at 9:13 AM Julien Grall <julien@xxxxxxx> wrote:
> >>
> >> Hi Tamas,
> >>
> >> On 21/02/2020 18:49, Tamas K Lengyel wrote:
> >>> +int libxl_domain_fork_vm(libxl_ctx *ctx, uint32_t pdomid, uint32_t 
> >>> *domid)
> >>> +{
> >>> +    int rc;
> >>> +    struct xen_domctl_createdomain create = {0};
> >>> +    create.flags |= XEN_DOMCTL_CDF_hvm;
> >>> +    create.flags |= XEN_DOMCTL_CDF_hap;
> >>> +    create.flags |= XEN_DOMCTL_CDF_oos_off;
> >>> +    create.arch.emulation_flags = (XEN_X86_EMU_ALL & ~XEN_X86_EMU_VPCI);
> >>
> >> This is x86 specific but seems to be written in common code. Did you
> >> build it on Arm?
> >
> > I have not, don't have a setup for ARM at the moment. I guess I'll
> > just move this function to libxl_x86.c to resolve the issue.
>
> It is fairly easy to setup a build environment for Arm. You can use QEMU
> user emulation and a Arm rootfs.
>
> >
> >>
> >>> +
> >>> +    create.ssidref = SECINITSID_DOMU;
> >>> +    create.parent_domid = pdomid;
> >>> +    create.max_evtchn_port = 1023;
> >>> +    create.max_grant_frames = LIBXL_MAX_GRANT_FRAMES_DEFAULT;
> >>> +    create.max_maptrack_frames = LIBXL_MAX_MAPTRACK_FRAMES_DEFAULT;
> >>
> >> The domain you fork may have different values here. From my
> >> understanding, the fork requires to have the same parameters as the
> >> parent. So how do you ensure they are the same?
> >
> > The parent domain is created by xl. If you create a domain with xl it
> > will have these parameters set by default.
>
> I hope you are aware that you can override most of those parameters in
> the guest configuration file. It would be good to at least write down
> the limitations so people doesn't spend ages figuring out why it does
> not work.

Fair enough.

Tamas

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